A multiple access communication system comprises a central controller, a shared transmission media and a plurality of remote terminals dispersed geographically. To provide the means for multiple access is a classical problem in communication systems with a shared common transmission media. Some of the well known schemes are frequency division multiple access or FDMA, time division multiple access or TDMA, and code division multiple access or CDMA. These multiple access schemes deal with the techniques of separating the communication bandwidth into traffic-bearing channels. In a FDMA scheme, the communication bandwidth is divided into the frequency bands. The TDMA scheme separates the communication bandwidth into time slots. The traffic is encoded and then decoded using different code in a CDMA scheme.
In all these multiple access schemes the contention for access is resolved through signalling protocols on a pre-determined and fixed signalling channel. There are proposals to dynamically allocate traffic-bearing channels to meet the service requirements in terms of lower blocking probability. However, in addition to availability, bandwidth and delay of the traffic-bearing channel, the traffic requirements should include responsiveness of the signalling process and the quality of the transmission means.
The signalling protocols for multiple access communication systems fall in two general categories for resolving the possible contention: scheduled access via polling or other means, and random access contention. In radiotelephony and local-area-network (CSMA/CD) environment, the contention is resolved by monitoring the signal during transmission, which requires synchronization and/or means to monitor activities amongst all remote terminals and the central controller. In the CATV network, remote terminals have different distance from the central controller making synchronization difficult. It is also not feasible to detect collision, i.e., multiple remote terminals transmit at the same time, on the CATV network since the remote terminals are attached to different branches of the network. The poll and response method is often used to schedule the multiple access from plurality of remote terminals, but it has the disadvantage of inefficiency due to wasteful interaction with remote terminals that are not in need of servicing.